1. Field of the Invention
The present invention relates, in particular, to an injection-molded resin bevel gear, among bevel gears transmitting rotational movement between two intersecting axes.
2. Description of the Related Art
Since the past, various bevel gears have been developed to perform power transmission between two intersecting axes in an automobile and the like. These various bevel gears have been put to actual use (refer to Patent Literature 1 and Patent Literature 2).
For example, to reduce deformation during quenching, a bevel gear 101 such as that shown in FIG. 12 includes a recess section 103 on a backside of a tooth 102. The thickness of a tooth root of the tooth 102 and the thicknesses of a rim-shaped section 104 and a flange section 105 are adjusted (refer to Patent Literature 1).
In a bevel gear 201 such as that shown in FIG. 13, to balance support rigidity of an inner end 202a side of a tooth 202 and support rigidity of an outer end 202b side of the tooth 202, reduce sudden deformation of the tooth 202 during meshing and rotational fluctuation attributed to the deformation, and reduce noise level, a balance recess 204 is formed on a support section 203 on the outer end 202b side of the tooth 202 (refer to Patent Literature 2).
In recent years, an injection-molded resin gear having reduced noise during power transmission, lighter weight, and being low in cost, as well as being capable of having higher accuracy, is receiving attention in industries related to precision instruments and precision machinery, and the like. Development of an injection-molded resin bevel gear having high accuracy and high rigidity is demanded.
Patent Literature 1: Japanese Patent Laid-open Publication No. Heisei 10-231917
Patent Literature 2: Utility Model-Laid-open Publication No. Heisei 5-50222
However, the bevel gear 101 shown in FIG. 12 is made of metal. Therefore, a technology related to a structure suppressing reduction in gear accuracy caused by shrinkage of resin after injection molding and securing sufficient rigidity is not disclosed. The bevel gear 101 cannot be applied to the development of the injection-molded resin bevel gear.
In the bevel gear 201 shown in FIG. 13, the thickness of the tooth 202 at the support section 203 differs greatly between the inner end 202a side and the outer end 202b side. Therefore, even when the bevel gear 201 is applied to an injection-molded bevel-gear, the amount of shrinkage after injection molding differs greatly between the support section 203 on the inner end 202a side and the support section 203 on the outer end 202b side. Therefore, a high level of gear accuracy cannot be acquired.